1. Field of Invention
This invention relates to the field of solar energy and lighting, and more specifically to using natural light for interior lighting.
2. Related Art
The transmission of concentrated solar energy via a light guide provides flexible options for numerous applications of solar lighting, solar heating, solar cooking, solar electric power generation, and photo physical and photochemical processes. Interior daylight lighting systems include windows and skylights, tubular solar lighting devices, and fiber optic solar lighting.
Fundamental problems remain, however, that keep solar lighting technology from widespread acceptance. Windows and skylight are limited by the shape and orientation of the building design. Solar light tubes suffer an extensive loss from collection and transmission limitations. Large diameter tubes are required because the light tube inlet is limited to collecting the solar light coming through its cross-section. Thereafter, the combined effect of multiple reflections along the length of the tube, with each reflection suffering a 5% to 15% reflection loss, diminishes the amount of light available at the outlet to less than 8% after a conservative 50 reflections in a solar light tube. Fiber optic bundles, while losing less light than solar tubes, are very expensive for general lighting applications.